Abstract: Project #1 The proportion of users of sweet-flavored and mentholated tobacco products (including menthol cigarettes) has increased dramatically, especially within the adolescent population, raising concerns that flavors may facilitate the initiation of tobacco product use and promote nicotine addiction. An additional concern is the recent introduction of synthetic cooling agents that may have effects similar to menthol. Children and adolescents are conditioned, through prior experience, to associate sweet and cooling flavors (fruit, candy, mints, etc.) with high sweetener content (sugar or artificial sweeteners). However, the role of flavors in the initiation of tobacco product use is difficult to study in humans, especially in adolescents and never-users. The goal of this project is to use our adolescent and adult rodent models of inhaled and smokeless tobacco product use, and of oral flavor-paired nicotine self-administration, to examine whether sweet and cooling flavors in tobacco products enhance nicotine use behavior and addiction. We will determine whether early flavor exposure and early flavorant associations with sweeteners influence subsequent nicotine choice and initiation, maintenance, and relapse to paired nicotine and flavorant intake. In Aim 1, we will examine sweet and cooling flavor exposure and conditioning effects on nicotine choice and use. In this aim, we will examine (A) the effects of conditioning to sweet flavors and cooling flavors on nicotine aversion and flavor preference and (B) the effects of characterizing sweet and cooling flavor exposure on the initiation and maintenance of nicotine-taking and relapse to nicotine-seeking. We will also use in-vivo voltammetry to examine reward-related dopamine signaling responses to flavorants, as these signals could serve as a biomarker for the ability of flavorants to enhance nicotine use and addiction. In Aim 2, we will examine the effects of synthetic cooling agents on respiratory irritation caused by electronic cigarette vapors ? effects that could potentially facilitate nicotine intake and use. The results of this work; (1) will provide the FDA with understanding of sweet and cooling flavor effects on the initiation and persistence of nicotine taking, and (2) could be used to guide policy decision on the regulation of sweet and cooling flavors in tobacco products.